I have generally stuck with one FI throughout my 97 hours of training, and it is general club procedure in my club to stay with one FI through the course. This is great for continuity and you get to know each others ways and in my case become good friends too.
I have also flown with our CFI and two other FIs when my chap wasn't available. They each have their own ways, but all teach the same (although the CFI teaches MDR for Nav whereas my FI, although he has taught MDR to his military students, has taught me the Whizz wheel way as for those of us who are mathematically challenged, its much easier!!)
So I think its whatever suits you best or whatever yout FTO advise. But personally, I would stick with the same FI as much as possible.